Typically, a solid oxide fuel cell (SOFC) employs a solid electrolyte of ion-conductive solid oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (MEA). The electrolyte electrode assembly is interposed between separators (bipolar plates). In use, normally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack.
As the fuel gas supplied to the fuel cell, normally, a hydrogen gas generated from hydrocarbon raw material by a reformer is used. In general, in the reformer, a reformed raw material gas is obtained from hydrocarbon raw material of a fossil fuel or the like, such as methane or LNG, and the reformed raw material gas undergoes steam reforming, partial oxidation reforming, or autothermal reforming to produce a reformed gas (fuel gas).
In this regard, a fuel cell system (fuel cell power supply apparatus) having a single unit case containing a fuel cell, a reformer, a power converter for converting direct power electrical energy generated in the fuel cell according to a power supply output specification, a control device, and auxiliary devices is known.
For example, in a fuel cell power supply apparatus disclosed in Japanese Laid-Open Patent Publication No. 2003-297409, as shown in FIG. 23, lateral bars 1001a, 1001b are provided in a frame 1001 of the unit case to divide the space in the frame 1001 into three stages. A reformer 1002 is provided on the lateral bar 1001a in the upper stage, and a control device 1003 and a fuel cell 1004 are provided on the lateral bar 1001b in the middle stage such that back sides of the control device 1003 and the fuel cell 1004 face each other. Heat insulating material 1003a is provided on the back surface of the control device 1003, and heat insulating material 1003b is provided around the control device 1003 to protect the control device 1003 from the ambient hot environment.
Auxiliary devices such as a fuel pump 1005 for supplying a raw fuel to a reformer 1002 and an air pump 1006a for supplying an air as a reactant gas to the fuel cell 1004 are provided on the bottom plate of the frame 1001. An air pump 1006b for a reformer burner is provided on an auxiliary rack 1001c at an upper position of the frame 1001, and a PG burner 1007 is provided in front of the air pump 1006b for the reformer burner. A power converter 1008 is provided on a side of the fuel cell 1004 on the floor of the frame 1001.
Further, for example, in a fuel cell apparatus disclosed in Japanese Laid-Open Patent Publication No. 2006-140164, as shown in FIG. 24, a package 1011 is provided, and a purifier 1012, an ion exchanger 1013, and a desulfurizer 1014 are provided adjacent to a front panel 1015 serving as an outer panel of the package 1011. The purifier 1012, the ion exchanger 1013, and desulfurizer 1014 are components that require maintenance.
Thus, the components that require maintenance are not provided inside the package 1011, but provided adjacent to the front panel 1015 serving as the outer profile of the apparatus body. According to the disclosure, in the structure, maintenance of the components that requires replacement, regeneration or the like for continuing operation of the fuel cell apparatus can be carried out easily.
In Japanese Laid-Open Patent Publication No. 2003-297409, the control device 1003 and the fuel cell 1004 are provided on the lateral bar 1001b in the middle stage of the frame 1001 such that the back sides of the control device 1003 and the fuel cell 1004 face each other. The control device 1003 should be used at relatively low temperature. However, the temperature of the fuel cell 1004 is raised by power generation. In particular, in the case where a high temperature fuel cell (such as a solid oxide fuel cell or a molten carbonate fuel cell) or a medium temperature fuel cell (such as a phosphoric acid fuel cell and a hydrogen membrane fuel cell) is used, the control device 1003 may be affected by heat depending on the heat insulating materials 1003a, 1003b. 
Further, in the system of Japanese Laid-Open Patent Publication No. 2006-140164, the operating temperature range and functions of the respective devices are not considered in the layout. Therefore, in particular, in the case where a high temperature fuel cell (such as a solid oxide fuel cell or a molten carbonate fuel cell) or a medium temperature fuel cell (such as a phosphoric acid fuel cell and a hydrogen membrane fuel cell) is used, the low temperature section which should be maintained at low temperature tends to be affected by diffusion of heat and fluid. Further, the desired maintenance performance cannot be achieved.